A METHOD FOR CORRECTING VERTICAL VELOCITIES MEASURED FROM A VESSEL-MOUNTED ACOUSTIC DOPPLER CURRENT PROFILER

Minor alignment errors (similar to 1 degrees) can contaminate acoustic Doppler current profiler measurements of vertical velocities taken fr om a ship traveling at speed. The signature is consistently large posi tive or negative vertical velocities, recorded at all depths. A techni que is proposed to postcorrect contaminated data in cases of tidally d ominated flow over a flat bottom. The eigenmodes of the cross-correlat ion matrix of the depth-averaged velocities are found, and the data ar e rotated to align along the eigenvector corresponding to the smallest eigenvalue that is equivalent to the physical vertical direction. An example of corrupted data is presented, and corrections for the pitch and roll directions are found. The corrected flow field is shown to be physically plausible over both flat and sloping bottom sections of th e cruise track.